Patent No. 5551016 Monitoring system and interface apparatus therefor

 

Patent No. 5551016

Monitoring system and interface apparatus therefor ( Loeb, et al., August 27, 1996)

Assignee: Queen's University at Kingston (Kingston, CA )

Abstract

In monitoring systems for acquiring data about a subject, such as are used, for example, in the medical, scientific and engineering fields, determination of temporal relationships between data acquired from multiple monitoring devices is facilitated by means of an interface unit which interconnects the monitoring devices with tape recorders for storing the data and a computer for processing the data. The interface unit generates various timing and control signals including a time code signal. The interface unit supplies the time code signal to the recording devices for recording simultaneously with the data. The time code signal may be a linear time code (LTC) derived from a video sync signal generated by the interface unit for synchronizing a camera. A sampling clock signal for controlling digitizing of the analog data acquired by the system is derived from the time code signal. The time code signal may comprise a common temporal reference signal, for example the SMPTE used with NTSC format video or its European equivalent EBU used with the PAL format. The video synchronization signal may itself be synchronized to and external timing signal, perhaps derived from one of the monitoring devices.

 

Notes:

FIELD OF THE INVENTION

The invention relates to monitoring systems comprising a plurality of monitoring devices for acquiring data about a subject for subsequent processing and/or analysis, and also to interface apparatus for use in such monitoring systems.

BACKGROUND

There are many applications in, for example, medical, scientific and engineering fields, where data acquired from multiple sources must be correlated so as to facilitate the determination of, for example, temporal relationships between events recorded in the data from the different sources. It is common to digitize and record these data according to discrete sampling periods. Data from the various devices and other equipment might be recorded using video/audio tape recorders and other equipment. Each piece of equipment would be connected, if necessary by way of a suitable interface, to a host or control computer which would control the equipment to collect and record data about events occurring during an experiment or a predetermined study period. The data would then be analyzed to determine, for example, the subject's responses to certain events occurring during the experiment or study period.

Some of the events may occur at irregular intervals with respect to each other and the sampling period, while other events may occur periodically but asynchronously with respect to each other and the sampling period. For example, in kinesiology experiments, events may be generated by electronic devices such as stimulators which operate autonomously producing events which are asynchronous with respect to the frame rate of the video camera. This makes it difficult to study the time course of the response of the system because the input event may have occurred at any time during the course of the video frame to which it is ascribed.

Several of the devices may each have an inherent frame rate which must be preserved, but which may not be compatible with each other (e.g. video and motion analysis systems employing North American NTSC and European PAL video formats) or may not provide adequate temporal resolution for digitizing data acquired simultaneously from other sources. Other items of the equipment might have their own internal time base, or no time base at all. Some equipment might use footage meters, others elapsed time, and others count sampling intervals. To find a particular portion of data may involve searching for sync pulses like tone pips and light flashes, which is tedious and often not reliable. Consequently, with such an assemblage of equipment, problems arise during analysis of the data when trying to determine what temporal correlation, if any, exists between events recorded by different ones of the monitoring devices.

SUMMARY OF THE INVENTION

An object of the present invention is to overcome or at least mitigate the problem.

According to one aspect of the present invention there is provided a monitoring system comprising a plurality of monitoring devices for acquiring data about a subject, an analog-to-digital converter means responsive to a sampling clock signal for digitizing data acquired by the monitoring devices, and interface apparatus for interconnecting the monitoring devices and the analog-to-digital converter means, the interface apparatus comprising timing means for generating a time code signal, deriving the sampling clock signal from, and synchronized to, the time code signal, and supplying said sampling clock signal to the analog-to-digital converter means.

According to a second aspect of the invention, there is provided interface apparatus for use in a monitoring system comprising a plurality of monitoring devices for acquiring data about a subject and analog-to-digital converter means responsive to a sampling clock signal for digitizing data acquired by the monitoring devices, the interface apparatus comprising timing means for generating a time code signal and deriving the sampling clock signal from, and synchronized to, the time code signal.

In preferred embodiments of either aspect of the invention, the monitoring system comprises at least one recording device for recording the acquired data and the interface apparatus further comprises means for supplying the time code signal to said recording device for simultaneous recording with the corresponding data.

Where the recording device is a multi-channel tape recorder, the time code supplying means may supply the time code signal to one of the channels.

The monitoring apparatus may comprise a video input device, such as a camera, which is responsive to a video synchronization signal and the interface unit comprise a video synchronization signal generator. The means for providing the time code signal may then be arranged to synchronize the time code signal and the video signal.

Where the system includes such a video input device, and at least one of the recording devices is a video recorder, for example a video tape recorder, the interface apparatus may comprise means for combining the time code with a video signal from a video monitoring device and supplying the combined signal to the video recorder. The combining means may then combine the time code as a vertical interval time code (VITC).

The time code signal may comprise a common temporal reference signal, for example the SMPTE used with NTSC format video or its European equivalent EBU used with the PAL format.

The signal generation signal circuit may be operable to start generating the video sync signal in response to a trigger signal, perhaps generated by operation of a push-button by the user. In addition, in some applications, the signal generation circuit may be responsive to an external synchronization signal, perhaps derived from one of the monitoring devices.

The interface unit may comprise means for supplying an analog signal from one of the monitoring devices to bin integration means comprising an integrator means for integrating the analog signal, sample-and-hold means for repeatedly sampling and storing the output of the integrator means, means for resetting the integrator means after each sampling by the sample-and-hold device, and variable offset full wave rectifier means for rectifying the analog signal before its application to the integrator.

The interface unit may comprise means for generating a time code signal comprising temporal data encoded onto a bit clock, and means for extracting a sampling clock for the analog-to-digital converter means from the time code signal.

A remote control unit may be provided to allow the user to operate the interface apparatus from a remote location. The remote control unit may comprise a video display, for example a liquid crystal display, and manual input devices such as keys and potentiometers, and be coupled to the interface apparatus by a link allowing transfer of video signals and data to the remote control unit and user-generated commands to the interface apparatus.

According to another aspect of the invention, apparatus for acquiring data from monitoring devices and conditioning the data for digitization by analog-to-digital converter means comprises means for supplying an analog signal from one of the monitoring devices to bin integration means comprising an integrator means for integrating the analog signal, sample-and-hold means for repeatedly sampling and storing the output of the integrator means, means for resetting the integrator means after each sampling by the sample-and-hold device, and variable offset full wave rectifier means for rectifying the analog signal before its application to the integrator.

Preferably, the apparatus further comprises means for selectively connecting the rectifier means in circuit with the integrator means.

According to another aspect of the invention, apparatus for acquiring data from monitoring devices and conditioning the data for digitization by analog-to-digital converter means comprises means for generating a time code signal comprising temporal data encoded onto a bit clock, and means for extracting a sampling clock for the analog-to-digital converter means from the time code signal.